The present invention relates to a display system and a method of producing the same, and particularly to a display system in which an insulation layer with semiconductor light-emitting devices as light sources embedded therein is thinned and a conductor film is provided on upper end portions of the semiconductor light-emitting devices exposed by the thinning, whereby upper end portion electrodes are led out, and a method of producing the same.
As a method of leading out an electrode of a semiconductor device covered with an insulation layer to the exterior, a method of forming a contact hole in the insulation layer by lithography, embedding a conductor material in the contact hole by, for example, a sputtering method and forming a conductor film on the surface of the insulation layer is widely conducted.
FIG. 17 shows a process of leading out an electrode 51 in a semiconductor device 50. FIG. 17A is a sectional view showing a silicon substrate 52 provided with the electrode 51 and a SiO2 insulation layer 53 provided on the surface thereof. In order to lead out the electrode 51 to the upper side of the insulation layer 53, a contact hole 54 is formed at the location where the electrode 51 is present, as shown in FIG. 17B. At this time, a positional deviation may occur between the contact hole 54 and the electrode 51. Furthermore, the probability of a positional deviation is greater as the electrode 51 is made smaller.
In order to fill the contact hole 54 with a conductor metal and provide a lead-out electrode on the upper surface of the insulation layer 53, sputtering or vapor deposition of a conductor metal 55 such as aluminum is carried out. However, the straight flying characteristics of the conductor metal particles, the conductor metal 55 tends to be deposited on a bottom portion of the contact hole 54, but not on the side wall, because the side wall is hidden by the conductor metal 55 which is deposited and grown on the inner peripheral portion of the top opening of the contact hole 54, as shown in FIG. 17C. As the process proceeds, connection failure may occur at the side wall portion of the contact hole 54. Alternatively, there may be difficulty in closing the opening at the top of the contact hole while leaving cavity on the inside of the contact hole 54, as shown in FIG. 17D.
In order to facilitate the connection described above, a method is known in the prior art in which the insulation layer is etched back. Namely, in Japanese Patent Laid-open No. Hei 7-142579, a contact wiring is adopted in place of the contact hole. FIG. 18 shows a process of connecting a lower layer wiring and an upper layer wiring by a contact wiring in the case of producing an image display system including surface conduction type electron emitting devices (SCE) as elements. As shown in FIG. 18A, a metal is electron beam vapor deposited on the lower layer wiring 62 provided on an insulating substrate 61, and unrequired portions are lifted up to form the contact wiring 63. Subsequently, as shown in FIG. 18B, an insulation film 64 of silicon oxide or the like is formed over the entire surface by a sputtering method. Further, as shown in FIG. 18C, a photoresist 65 is formed over the entire surface. Thereafter, as shown in FIG. 18D, etching back for flattening is conducted to expose the surface of the contact wiring 63, and, as shown in FIG. 18E, an upper layer wiring 66 is provided. Thus, a multilayer wiring is disclosed. However, this method exposes the contact wiring, not the semiconductor light-emitting devices.
Japanese Patent Laid-open No. Hei 7-94124 discloses a method of producing light-emitting devices in a display system including electric field emission cathodes. As shown in FIG. 19A, a cathode chip 70a is provided on a main surface of a substrate 70, and, as shown in FIG. 19B, an insulation layer 72 and an anode layer 73 are sequentially provided on the substrate 70 by sputtering. Further, as shown in FIG. 19C, a fluorescent material layer 74 is provided by sputtering. Then, as shown in FIG. 19D, a polyimide resin layer 75 is deposited to cause flattening, and thereafter, the polyimide resin layer 75 is etched back to expose a protuberant portion of the fluorescent material layer 74, leaving the polyimide resin layer 75 therearound. Then, as shown in FIG. 19E, the fluorescent material layer 74, the anode layer 73 and the insulation layer 72 are sequentially selectively etched using the polyimide resin layer 75 as a mask, whereby the cathode chip 70a is exposed. However, this method has the exposure of the cathode chip itself as an object, and is not for leading out the upper end portion electrode of the semiconductor light-emitting device exposed.
The present invention has been made in consideration of the above described limitations of the prior art. Accordingly, it is an object of the present invention to provide a display system including semiconductor light-emitting devices disposed on and fitted to a substrate surface and covered with an insulation layer, in which upper end portion electrodes of the semiconductor light-emitting devices are led out easily and securely. The invention further includes a method of producing the same.
The above-mentioned problems can be solved by a first aspect or a second aspect of the present invention. The inventive solutions will be described below.
In accordance with a first aspect of the present invention, there is provided a display system including multiple semiconductor light-emitting devices disposed on and fitted to a substrate surface. An insulation layer with the semiconductor light-emitting devices embedded therein is thinned selectively or non-selectively. Further, a conductor film is provided on upper end portions of the semiconductor light-emitting devices which are exposed by the thinning, and upper end portion electrodes of the semiconductor light-emitting devices are led out to an upper surface of the insulation layer. Unlike display systems in which a contact hole for leading out the upper end portion electrode onto the insulation layer is not provided, the display system of the present invention is free of the positional deviation problems between the contact hole and the upper end portion electrode and contact failure in the contact hole. Thus, the upper end portion electrodes of the semiconductor light-emitting devices are connected easily and securely.
Preferably, there is provided a display system in which the insulation layer is formed of a high polymeric compound capable of forming a coating film containing a polyimide resin, an epoxy resin or a synthetic rubber or a glass capable of forming a coating film. In such a display system, the insulation layer is formed by application, so that the insulation layer can be easily formed even in the case where the area of the substrate surface is large, and the display system is reduced in cost.
Preferably, there is provided a display system in which the insulation layer is composed of silicon oxide or silicon nitride formed by a CVD (chemical vapor deposition) method or a sputtering method. Such a display system shows excellent heat resistance owing to the insulation layer composed of the inorganic material.
Preferably, there is provided a display system in which the thinning of the insulation layer is carried out by a dry etching method under an oxygen plasma atmosphere, a chemical mechanical polishing method or a combination of both methods. In such a display system, a most appropriate method is selected according to the kind of material of the insulation layer adopted and the conditions of the thinning.
Preferably, there is provided a display system in which the semiconductor light-emitting device has a primary light-emitting direction in a direction from a light-emitting region toward a lower end surface on the substrate surface, and has a reflective surface for downward reflection at a portion above the light-emitting region. In such a display system, the light emitted from the semiconductor light-emitting device is effectively directed in the light-emitting direction toward the lower end surface by the reflective surface.
Preferably, there is provided a display system in which the semiconductor light-emitting device is formed in a pyramid shape or a truncated pyramid shape, and at least one slant surface of surfaces thereof is the reflective surface. In such a display system, a slant surface of the pyramid or truncated pyramid and an upper surface also in the case of the truncated pyramid, are reflective surfaces, so that the light emitted can be concentrated to the lower end surface side.
Preferably, there is provided a display system in which the semiconductor light-emitting device is composed of a hexagonal crystal of a gallium nitride semiconductor, and includes at least an active layer, namely a light-emitting region, parallel to (1,xe2x88x921,0,1) plane. In such a display system, the active layer parallel to (0,0,0,1) plane of the gallium nitride semiconductor has a high light-emitting efficiency, and an electrode surface provided on (1,xe2x88x921,0,1) plane can be made to be a reflective surface, so that excellent light-emitting performance is obtained.
Preferably, there is provided a display system in which the semiconductor light-emitting device is composed of a gallium nitride semiconductor selectively grown in a hexagonal pyramid shape or a truncated hexagonal pyramid shape with (0,0,0,1) plane as the lower end surface and with (1,xe2x88x921,0,1) plane and an equivalent surface as the slant surface, on a substrate surface of growth, and includes an active layer parallel to (1,xe2x88x921,0,1) plane and an equivalent surface. In such a display system, the active layer parallel to (1,xe2x88x921,0,1) plane of the gallium nitride semiconductor has a high light-emitting efficiency, and an electrode surface provided on (1,xe2x88x921,0,1) plane can be made to be a reflective surface, so that the light emitted is concentrated to the lower end surface side, and a display system with high luminance is provided.
Preferably, there is provided a display system in which the display system is an image display system or an illumination system including the semiconductor light-emitting devices which emit monochromic light or a combination of a plurality of kinds of semiconductor light-emitting devices which emit different-colored lights. Such a display system provides a clear or a clear and colorful image or illumination.
Preferably, there is provided a display system in which the semiconductor light-emitting devices each include a first conduction type semiconductor layer, an active layer and a second conduction type semiconductor layer sequentially laminated, the upper end portion electrode is formed at the second conduction type semiconductor layer, and the upper end portion electrode and the conductor film are formed of the same kind of metal. In such a display system, a lead-out electrode composed of the conductor film and the upper end portion electrode are jointed rigidly and stably.
Preferably, there is provided a display system in which the semiconductor light-emitting devices each include a first conduction type semiconductor layer, an active layer and a second conduction type semiconductor layer sequentially laminated, the insulation layer is thinned, and the conductor film is formed on a surface formed of the second conduction type semiconductor layer exposed by the thinning and the insulation layer, whereby the upper end portion electrode and the conductor film are formed as one body with each other. In such a display system, fitting of the upper end portion electrode to the second conduction type semiconductor layer and formation of the conductor film are carried out simultaneously, so that the number of steps is reduced, and cost is thereby reduced.
Preferably, there is provided a display system in which the semiconductor light-emitting devices each include a first conduction type semiconductor layer, an active layer and a second conduction type semiconductor layer sequentially laminated, the upper end portion electrode is provided on the second conduction type semiconductor layer with a contact metal layer of a predetermined thickness therebetween, and the upper end portion electrode and the conductor film are formed of the same kind of metal. In such a display system, a lead-out electrode composed of the conductor film and the upper end portion electrode are jointed rigidly and stably, the reflectance of the upper end portion electrode is high, and the reflected light is concentrated into an emitted light pick-up direction, so that light-emitting efficiency is high.
Preferably, there is provided a display system in which the semiconductor light-emitting devices each include a first conduction type semiconductor layer, an active layer and a second conduction type semiconductor layer sequentially laminated, a contact metal layer of a predetermined thickness is formed on the second conduction type semiconductor layer, the insulation layer is thinned, and the conductor film is formed on a surface formed of the contact metal layer exposed by the thinning and the insulation layer, whereby the upper end portion electrode and the conductor film are formed as one body with each other. In such a display system, the reflectance of the upper end portion electrode is high, the reflected light is concentrated into an emitted light pick-up direction, light-emitting efficiency is therefore high, and, further, the upper end portion electrode and the conductor film are formed as one body with each other, so that the number of steps is reduced, and production cost is lowered.
In accordance with a second aspect of the invention, there is provided a method of producing a display system by disposing and fitting multiple of semiconductor light-emitting devices to a substrate surface, including the steps of embedding the semiconductor light-emitting devices in an insulation layer, selectively or non-selectively thinning the insulation layer to expose upper end portions of the semiconductor light-emitting devices, and forming a conductor film on the exposed upper end portions, whereby upper end portion electrodes of the semiconductor light-emitting devices are led out to an upper surface of the insulation layer. According to such a method of producing a display system, a contact hole is not provided in the insulation layer covering the semiconductor light-emitting devices, so that the troubles of positional deviation between the contact hole and the upper end portion electrode of the semiconductor light-emitting device and contact failure in the contact hole are absent, and the upper end portion electrodes of the semiconductor light-emitting devices can be lead out to the upper surface of the insulation layer easily and securely.
Preferably, there is provided a method of producing a display system in which the insulation layer is formed by application of a high polymeric compound capable of forming a coating film containing an epoxy resin, a polyimide resin or a synthetic rubber or a glass capable of forming a coating film. According to such a method of producing a display system, the insulation layer can be easily formed even where the area of the substrate surface is large.
Preferably, there is provided a method of producing a display system in which the insulation layer is formed by building up silicon oxide or silicon nitride by a CVD method or a sputtering method. Such a method of producing a display system gives a display system high in heat resistance temperature owing to the insulation layer formed of the inorganic material.
Preferably, there is provided a method of producing a display system in which the insulation layer is thinned by a dry etching method under an oxygen plasma atmosphere, a chemical mechanical polishing method or a combination of both methods. According to such a method of producing a display system, a most appropriate method can be adopted according to the kind of material of the insulation layer and the conditions of the thinning.
Preferably, there is provided a method of producing a display system in which semiconductor light-emitting devices each having a primary light-emitting direction in the direction from a light-emitting region toward a lower end surface on the substrate surface and including a reflective surface for downward reflection at a portion above the light-emitting region are used as the semiconductor light-emitting devices. According to such a method of producing a display system, the emitted light is effectively directed toward the lower end surface by the reflective surface of the semiconductor light-emitting device, thereby enhancing the luminance of the display system.
Preferably, there is provided a method of producing a display system in which semiconductor light-emitting devices which are formed in a pyramid shape or a truncated pyramid shape and in each of which at least one slant surface of surfaces thereof is the reflective surface are used as the semiconductor light-emitting devices. According to such a method of producing a display system, a slant surface of the polygonal pyramid or truncated polygonal pyramid, and the upper surface also in the case of the truncated polygonal pyramid, are reflective surfaces, whereby the light emitted by the semiconductor light-emitting device can be concentrated to the lower end surface side.
Preferably, there is provided a method of producing a display system in which semiconductor light-emitting devices each composed of a hexagonal crystal of a gallium nitride semiconductor and having an active layer parallel to (1,xe2x88x921,0,1) plane are used as the semiconductor light-emitting devices. According to such a method of producing a display system, the active layer parallel to (1,xe2x88x921,0,1) plane of the gallium nitride semiconductor light-emitting device shows a high light-emitting efficiency, so that a display system with excellent light-emitting performance is provided.
Preferably, there is provided a method of producing a display system in which semiconductor light-emitting devices each composed of a gallium nitride semiconductor selectively crystal-grown in a hexagonal pyramid shape or a truncated hexagonal pyramid shape with (0,0,0,1) plane as the lower end surface and with (1,xe2x88x921,0,1) plane and equivalent surfaces as the slant surfaces, on a substrate surface of growth, and including active layers parallel to (1,xe2x88x921,0,1) plane and equivalent surfaces are used as the semiconductor light-emitting devices. According to such a method of producing a display system, the active layer shows a high light-emitting efficiency, and an electrode surface provided on (1,xe2x88x921,0,1) plane functions as a reflective surface to concentrate the emitted light to the lower end surface side, so that a display system with a particularly high luminance is provided.
Preferably, there is provided a method of producing a display system in which the semiconductor light-emitting devices each including a first conduction type semiconductor layer, an active layer and a second conduction type semiconductor layer sequentially laminated, and each including an upper end portion electrode formed at the second conduction type semiconductor layer are used as the semiconductor light-emitting devices, and the conductor film is formed of the same kind of metal as the upper end portion electrode. According to such a method of producing a display system, a lead-out electrode composed of the conductor film and the upper end portion electrode are jointed rigidly and stably.
Preferably, there is provided a method of producing a display system in which the semiconductor light-emitting devices each including a first conduction type semiconductor layer, an active layer and a second conduction type semiconductor layer sequentially laminated are used as the semiconductor light-emitting devices, the insulation layer is thinned, and the conductor film is formed on a surface formed of the second conduction type semiconductor layer exposed by the thinning and the insulation layer, whereby the upper end portion electrode and the conductor film are formed as one body with each other. According to such a method of producing a display system, the upper end portion electrode and the conductor film are formed as one body with each other, and the fitting of the upper end portion electrode to the second conduction type semiconductor layer and the formation of the conductor film are carried out simultaneously, so that the number of steps is reduced, and a display system low in cost is provided.
Preferably, there is provided a method of producing a display system in which the semiconductor light-emitting devices each including a first conduction type semiconductor layer, an active layer and a second conduction type semiconductor layer sequentially laminated, and each including an upper end portion electrode formed on the second conduction type semiconductor layer with a contact metal layer of a predetermined thickness therebetween are used as the semiconductor light-emitting devices, and the conductor film is formed of the same kind of metal as the upper end portion electrode. According to such a method of producing a display system, the reflectance of the upper end portion electrode is high, the reflected light is concentrated into an emitted light pick-up direction, thereby enhancing the light-emitting efficiency, and a lead-out electrode formed of the conductor film and the upper end portion electrode are jointed rigidly and stably.
Preferably, there is provided a method of producing a display system in which the semiconductor light-emitting devices each including a first conduction type semiconductor layer, an active layer and a second conduction type semiconductor layer sequentially laminated and each including a contact metal layer of a predetermined thickness are used as the semiconductor light-emitting devices, and the conductor film is formed on a surface formed of the contact metal layer exposed by thinning of the insulation layer and the insulation layer itself, whereby the upper end portion electrode and the conductor film are formed as one body with each other. According to such a method of producing a display system, the reflectance of the upper end portion electrode is high, and the reflected light is concentrated into an emitted light pick-up direction, so that light-emitting efficiency of the display system is enhanced. Furthermore, the upper end portion electrode and the conductor film are formed as one body with each other, and the fitting of the upper end portion electrode to the second conduction type semiconductor layer and the formation of the conductor film are carried out simultaneously, so that the number of steps is reduced, and the cost of the display system is thereby lowered.
The above and other objects, features and advantages of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings which show by way of example some preferred embodiments of the invention.
Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the Invention and the figures.